1. Field of the Invention
The present invention relates to an object, a method, or a manufacturing method. Further, the present invention relates to a process, a machine, manufacture, or a composition of matter. In particular, the present invention relates to a semiconductor element, a semiconductor device, and a method for manufacturing a semiconductor element.
In this specification, a semiconductor device generally means a device which can function by utilizing semiconductor characteristics, and an electro-optic device, a semiconductor circuit, and electronic equipment are all semiconductor devices.
2. Description of the Related Art
Transistors including a semiconductor thin film which is formed over a substrate having an insulating surface and serves as an active layer are widely used in electronic devices such as integrated circuits (ICs) and image display devices (display devices). A silicon-based semiconductor material is widely known as a material for a semiconductor thin film applicable to a transistor. As another material, an oxide semiconductor has been attracting attention.
For example, a thin film transistor in which an oxide semiconductor including an In—Ga—Zn-based oxide is used for an active layer is disclosed (see Patent Document 1).